[unreadable] The long term goal of this investigation is to develop a small animal SPECT/CT system that provides a significantly improved imaging performance for small animal models of human diseases with I-125 labeled radiotracers. This development makes use of the recently developed and commercially available Electron Bombarded Charge Coupled Device (EBCCD) technology. Compared with the position sensitive photomultiplier (PSPMT) tubes, it offers an order of magnitude improvement in the spatial resolution for detecting low energy gamma rays. This advance in detector technology may be translated into better estimates of the tracer distributions within test animals. In order to achieve this long-term goal, two specific aims are proposed for the project period: [unreadable] [unreadable] 1. Experimentally demonstrate that the EBCCD device is capable of providing a significant improved spatial resolution for detecting low energy gamma rays from 1-125. The expected key performances include (1) an intrinsic spatial resolution of ~0. 1mm, (2) a signal level of ~5 photoelectrons for gamma rays with 30keV and (3) a total noise level significantly lower than the signal induced by 1-125 gamma rays. [unreadable] [unreadable] 2. Demonstrate that the very high resolution of the EBCCD device can be translated into much improved imaging performance for SPECT/CT imaging. We will to show this improvement in two ways. First, we would like to construct a prototype SPECT/CT system that will be tested in experimental performance assessments. Second, we would like to compare the actual system performance with that predicted analytically with theoretical tools previously developed in the University of Michigan. This would help us to gain insights into the requirements and suitable design tools for future development of small animal imaging systems. [unreadable] [unreadable] This investigation will also create opportunities for collaborative studies with investigators of the University of Michigan's SAIRP, the Department of Veterans Affairs Healthcare System at Ann Arbor and CERN. [unreadable] [unreadable]